Any insect that flies at night must deal with bat predation. Take a moth, for example. Moths arrived first on the evolutionary stage; when much later on bats appeared with their sophisticated apparatus for echolocating prey, moths were forced to change or die. Some species developed ears to hear the approach of a bat; this generally evokes evasive flight maneuvers like loops and dives. Other species acquired distasteful chemicals that gave them a repugnant or poisonous taste. Some even developed the ability to produce sounds that seem to confuse, and sometimes thwart, an attacking bat.
You may know that the recently-released UltraVox XT 3 is used to study ultrasound vocalizations, especially in rodents and bats. But the fact that it analyzes full-spectrum sound, together with the filter options and cool features like the spectrogram and the automatic call detection, makes it ideal for analyzing bird calls. Yours truly must admit that he is not fond of quantification of behavior at any cost, but this time he could not resist.